NC0036404_Managing Sprayfields_20030501

— Soil Fertility Note 15
Managing Bermudagrass Sprayfields
May 2003
NCDA&CS Agronomic Division
www.neagr.govtagrononii
Serving North Carolina growers since 1940
Phone: [phone]
Decline and loss of hybrid bermudagrass stands on swine
farm wastewater sprayfields is an increasing concern
on sites that are overseeded with a winter annual (WA)
grass and managed for hay. Many swine operations
must overseed their sprayfields due to limited wettable
acreage. Overseeding every fall is a viable and useful
practice on pastureland where forage is grazed by
animals. However, it can be problematic on fields where
forage is mechanically harvested.
Growth and Development of Bermudagrass
Hayfields and pastures differ in sward, or stand thickness.
Hybrid bermuda hayfields normally exhibit moderate -
to low -sward density, as measured by the number of
growing points close to the ground surface. Hayfields
generally have erect stems with few stolons (runners)
and few rhizomes (underground stems).
Pastures, however, have many stolons and rhizomes.
Each node on a stolon can develop roots, leaves, erect
stems, and other stolons—the more light they receive,
the more they grow. Rhizomes develop in response to
defoliation (cutting or grazing) and fertility and store
the carbohydrate reserves produced by photosynthesis.
Effects of Annual Overseeding
When soil surface growing points are deprived of light
for long periods (as in overseeded hayfields), the number
of growing points decreases. That is why bermudagrass
develops erect stems in hayfields. As stems elongate and
compete for light, the sward thins. Swards that contain
few rhizomes and stolons have less reserve energy and
may deplete their carbohydrate reserves iftransition from
dormancy is delayed.
It is not advisable to overseed a bermuda hayfield
more than once every two years. Introducing a winter
annual (WA) overseed into a hayfield adds competitive
stress, and overseeding every year can significantly
reduce bermuda stands. However, since rotating winter
overseeding among fields is not possible under most
waste plans, early removal of the WA is critical. When the
WA remains on too long, bermuda expends root reserve
energy in an effort to grow as warm soil temperatures
stimulate its transition from dormancy.
Warm spring air and,soi1 temperatures also trigger
germination of summer1annual grasses and weeds. When
WA harvest is delayed, competition from summer annuals
can overwhelm weakened bermuda. In a healthy stand,
"green -up" typically begins before summer annuals
emerge, and bermuda competes well.
On sprayfields, re-establishment of bermuda can
be problematic. The need to remove the WA often
interferes with timely re -sprigging of fields, which is
best done in March when sprigs are dormant. Waste plan
compliance often requires even newly re -sprigged fields
to be overseeded in the fall. Overseeding in the year of
establishment can severely stress bermuda, especially if
sprigs are planted late (May, June).
Tips for Protecting Bermudagrass Stands in
Sprayfields
•
•
Always use an early maturing cereal, such as rye,
to overseed sprayfields. Choose an erect cultivar,
such as `Abruzzi,' 'land seed at 75-90 lb/acre drilled
no -till or at 100+ lb/acre broadcast.
Do not use annual ryegrass or the leafier
grazing -type ryes, except when overseeding
pastures. Oats have intermediate maturity but tend
to produce leafier; and more competitive regrowth
than rye or triticaie. Wheat matures late and is not
well adapted as an overseed.
Use good seed. Certified seed is best, but if you
use non -Certified 'seed, especially in bulk, store it
properly and have the germination tested by the
NCDA&CS Plant Industry Division. Having this
test done prior to purchase can avert stand failures
and disputes over seed quality.

•: Harvest the WA on time, ?yen if weather is less than)
ideal. Remove the overseed at the "boot"stage of)
growth —prior to emergence of seed heads from the
sheath. For rye, this is usually early April but varies
with species and weather. In some years, follow-up
harvests of the WA may be needed.)
Early April is seldom a good time to dry hay
in the field, so plan to remove the WA as chopped
or baled silage. Timely harvest of the WA permits
bermuda to emerge from dormancy and develop
leaf area before summer annual grasses and weeds
germinate. If annual ryegrass was sown, plan on
multiple harvests. A herbicide (metsulfuron) may
be warranted for heavy regrowth.
•• Harvest bermudagrass at least every four weeks ❖ Iunder a normal rainfall and nitrogen fertility
regime. Light must reach the lower stems to promote
stolon development and increase density of growing
(points. Frequent harvests also reduce competition by)
(removing weedy grasses.)
• Fertilize appropriately to help bermuda compete
with weeds. At green up, bermuda needs 25-40 lb/
acre nitrogen, potassium as recommended by a soil
test (minus that supplied by waste irrigation), and on
sands, 10-20 lb/acre sulfur. Phosphorus is not needed
or desired on most sprayfields. Waste applications
usually provide the needed nutrients; however, if
there is insufficient waste to supply enough nitrogen,
amend your waste utilization plan to allow a modest
application of commercial fertilizer. Apply any
supplemental fertilizer in mid -April to mid -May.
❖ (Apply lime according to a NCDA&CS soil testa ❖
During establishment, apply and incorporate all
recommended lime before sprigging. In subsequent
maintenance applications, lime will have to be
surface applied and will move through the soil profile
very slowly. If a soil report recommends more than
one ton per acre, apply one ton immediately and the
balance the following year. The target pH for hybrid)
(bermuda is 6.5.)
On deep sandy soils, test for nematodes before
establishing a stand or if existing stands are poor.
Although nematodes are not usually a problem in
bermudagrass, sting nematodes can be damaging in
highly sandy soils, especially when soils are moist
and soil temperatures are cool. Affected plants have
stubby roots, and stands are thin.
Cultural practices are the only way to manage sting
nematodes in forage grasses. Timely delivery of
water and nutrientsfrom waste irrigation helps crops
compensate for root damage. However, managers
must be aware that timely management of the
bermudagrass and WA overseed is even more critical
when nematodes are present.
Control weeds and insects. The best and most
cost-effective weed control is timely management
of bermudagrass and the WA overseed along with
common-sense cultural practices. A well -managed
hayfield is competitive and rarely needs herbicide.
Fall armyworms are leaf feeders and can cause
severe. defoliation.. Multiple outbreaks may occur in
a season, and infestations seem to be worse in dry
years. Armyworm ;damage can rob a grower of one
or more hay cuttings.
Grubs feed on roots and can cause damage in
large patches or small isolated spots. Treatment is
rarely justified but Inlay be advisable on sprayfields
where weak stands, are being managed for recovery.
September is the best time to treat fields.
Consult the N. C. Agricultural Chemicals
Manual and product labels for restrictions and rates
pertaining to herbicides and insecticides.
Call your regional agronomist. Agronomists make
on -site visits, assist with nutrient management
problems, and give advice on taking samples and
interpreting and implementing recommendations.
Call 919-733=265I5 or visit the Web page www.
ncagr.gov/agronomi/rahome.htm to find contact
information for your area agronomist.
'!Tim Hall, Regional Agronomist
Questions or comments should be directed to the Soil Testing Section of the NCDA&CS Agronomic Division.
Information on field services, nematode assay and plant/waste/solution/media analyses
is also available from the division. :
Steve Troxler, Commissioner of Agriculture